1. Background:
Aortic regurgitation – or aortic insufficiency – is a disease of the aortic valve whereby blood from the aorta leaks across the valve into the left ventricle during diastole when the valve should be closed. The amount of blood that leaks across the valve during diastole is the regurgitant volume.
2. Benefits of cardiac MRI use:
Cardiac MRI is well suited for the examination of aortic regurgitation because it can accurately quantifiy the regurgitant volume, and left ventricular size and function. It is totally non-invasive and does not require contrast.
3. MRI technique:
Short and long axis SSFP images are obtained to quantify end-diastolic and end-systolic LV volumes from which one can calculate the ejection fraction.
Phase-contrast images are obtained perpendicular to the aorta just distal to the aortic valve.
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For accurate results, an identically prescribed phase-contrast image of a stationary phantom is used for baseline correction of the flow data.
To assess valve anatomy such as the number of cusps, SSFP images are acquired through the valve perpendicular to the aortic root.
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4. Analysis:
The simplest and most direct way to determine the regurgitant volume is by integrating the area under the aortic flow vs. time curve during diastole. There are other methods which can be used to confirm the magnitude of the regurgitation, but they are based on various assumptions.
The best way to determine the regurgitant fraction is to divide the regurgitant volume by the LV stroke volume.
Flow vs. time
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5. Which imaging findings affect treatment?
The severity of aortic regurgitation can be quantified in terms of regurgitant volume or regurgitant fraction. Surgery is generally reserved for patients with severe aortic regurgitation unless they are going for cardiac surgery for other reasons. Surgical timing generally depends on symptoms, LV ejection fraction, and LV dimensions. AHA guidelines are shown in detail here.
The criteria for classification of aortic regurgitation are as follows:
| Regurgitant Volume | Regurgitant Fraction | |
| Mild | <30 ml/beat | <30% |
| Moderate | 30-60 ml/beat | 30-50% |
| Severe | >60 ml/beat | >50% |
6. Drawbacks of other tests:
Echocardiography is most commonly used to assess the severity of aortic regurgitation. It is also used to assess LV size and function. However, the assessment is usually qualitative and operator dependent. The assessment can be more difficult in patients with eccentric or multiple jets, or patients with multivalvular disease.
7. Sample report:
